Conventional sailboards include a board with an upper or deck face or surface on which a number of foot locating stirrups or straps are provided and which has a support base for supporting the rig. On the bottom or water side of the board a fixed rudder or fin is provided.
The two hydraulic forces employed to turn a sailboard are firstly, tilting the rig to move the centre of effort of the sail to provide a turning moment in the required direction. Secondly, if the board has reasonable speed, digging a rail will increase the velocity of water flow on one side of the board inducing a lower pressure and a turning force.
When tacking or gybeing any sail powered craft, it is desirable to get the craft on the next tack with sail set as quickly as possible in order to:
a. Minimise the loss of "windage".
b. Minimise the time taken to turn.
c. To avoid the lack of control when sailing very close to the wind.
Most sail powered craft use a rudder, which deflects the water flowing past it and by Newton's second law of action and reaction, a powerful hydraulic force is employed to turn the craft. The problem with a sailboard is that with both hands on the boom, to suggest a hand held tiller is impractical.
A sailboard is used in many different conditions from smooth lake to rough sea, so an effective rudder must be controllable at speed and when the board is bouncing over choppy waves.
The vast majority of boardsailors and hence board purchasers are reasonably affluent, sail perhaps once a week for 20 weeks in a year on large (3 to 4 meter) boards on flat water. Most sailors cannot waterstart and are probably not very fit. So a sailing session is limited by the number of times they fall off and subsequently have to uphaul the sail. Most falls occur during the turn (a board with a low volume tail will perform well, but when slowed half way through a poor gybe becomes very unstable and likely to put the sailor into the water). It follows that an innovation that makes turning easier, faster and more successful can be developed can assist in overcoming the disadvantage inherent in conventional sailboards.
It is an object of the invention to suggest steering means for such rudders and also to a board including such steering means.